Process for the preparation of formic acid from the reaction mixture of formates and mineral acid.



J. WBISE. PROCESS 3011 THE PREPARATION OF FORMIG ACID FROM THE REAOTION MIXTURE 0F FORMATES AND MINERAL ACID.

APPLICATION FILED JULY 10, 1012.

1,043,985. Patented Nov. 12, 1912.

UNITED say-urns PATENT osmon.

JULIUS wnrsn, or :WIESBADEN.

GERMANY, ASSIGNOR TO THE rmivror RUDOLPH KOEPJ? & 60., OF OESTRICH-ON-THE-RHINE, GERMANY.

F FORMATES AND MINERAL AC1...

Specification of Letters Patent.

Patented Nov. 12, 1912.

Application filed July 10, 1912. Serial No. 708,653.

' To all whom it may concern:

'- Be itknown that I. JULIUS Weiss, a sub- .jcctof the German Emperor, and resident "mass breaks up into a through leaks,

- tain new 7 -esses for the Preparation'of Formic Acid .from the Reaction Mixture of Formates and Acid, of which the following is aof' \Vicsbaden, Germany, have invented cerand useful Improvements in Proc- Mineral specification.

The object of the present invention is a process 'f(' the preparation of formic acid with a-yield which coul'dnot be attained hitherto.

It is well-known that formic acid is prc-= .par'ed by mixing sodium formate with su1-' .furic acid. .Int i .or paste is formed sodlum sulfate and liquid formic acid. If the latter is distilled ofl", then under heats process a very thick pulp consisting of pulverulent ing the pulp or pa'ste.the distillation is fairly rapid at first. $oon, however, the moist powder, and then the process does not proceed any fun ther. In order to carry overthe still remaining ,formicacid into the receiver hitherto a vacuum has been made use of. This however has essential drawbacks, because with the use of a vacuum when manufacturing on a large scale it is, as is Well-known, not possible to so close the apparatus that air does not continually get intothe vacuum so that the air pumphas to be continually kept working. This is of little consequence for ordinary working processes and only requires a greater c0nsumption of power, viz., for keeping the air pump continually going. However, when preparing formic acid this is different. ormic acid has such an ailinity for air that it can be only separated from same with difficulty, and that such a separation in an efiicient manner is even practically impossible. In consequence of this when using a vacuum a very considerable amount of formic acid is carried away by the air pump with the evacuated air. This amount is so considerable that the preparation of formic acid as hitherto effected was very unsatisfactory economically, but nevertheless the industry knew no other means for obtaining a more economical yield.

1 In consequence of the above-n'ientioned reof the failure of a vacuum for this purpose, there remains no other means for the worksmanager than the well-known method of effecting the distillation with the use of a strong current of a volatile substance which mechanically carries with it the body to be distilled oil.

The employment of a mechanically acting current of steam, used in similar cases is entirely excluded in the present case, as the use of such current of steam would dilute the formic acid, in a most undesirable manner. It suggests itself to use for the purpose in question instead of a current of steam, a. strong current of air. Against this, however, stands the, teat obstacle of the already mentioned a V nity of formic acid for air, which renders impossible a subsequent separation of the air from the formic PBQCE SS FOR THE PREPARATION FORMIC ACID FROM THE REACTION MIXTURE acid carried therewith and thus leads to large losses of formic acid. Now it has been found that this obstacle can be effectively overcome, and that it is possible to carry out the preparation of formic acid from formates and mineral acids with an almost theoretical yield, by inserting in a manner already known in other industries the whole distillation apparatus: reaction vessel, cooling coil, receiver for the liquid formic acid, into the closed circuit of one and the same air current constantly kept in motion by a ventilator or the like.

. The air current is for instance driven by the-ventilator into the there through the cooling coil, and then into the receiver from there to return to the ventilator, and to assume its new course through the apparatus. In .this case the circulating air acts in such manner that it dissovles the formic acid adhering as moisture to the sodium sulfate and always takes the same up again to the saturation point, then to give it off in the cooling device. In the latter it naturally only gives oil that part of the acid which the hot saturated air-acid-mixturc issuing from the distilling vessel can no longer retain at the saturation temperature prevailing in the cooling vessel, but this does not adversely effect the ultimate reaction vessel, from yield of acid, in consequence of the continu ous cyclic motion of the mixture. It is evident that always the same amount of air is driven through the apparatus and the formic acid carried with the air but not condensed iu the cooling vessel, is always led back lnto the reaction vessel; By suitably closing off the various vessels against the atmosphere care is taken that outerairdoes not get to'the circulating current of action vessel bythe tube (1. The air de-- livered by the ventilator flows from b to the cooling coil 6 carrying with it the gaseous formic acid formed and then flows to the receiver 9 from where it returns through.

the suction tube 71- to the ventilator c and stead of airnaturally other gases can be employed which are indifi'erent to the dis-' thence into the reaction chamber 6. This arrangement has given, Very satisfactory results in practice. The distillation is efitected in a surprisingly rapid manner, a loss'is, prevented, as any acid carried away from the receiver is led back into the reac-' tion chamber as already explained. In-

tillate'. p

In the literature already processes have become known according -to which the distillat-ion of certain substances is eife'cted in a cyclic process with the use of inert-gases. However, it has not become known to employ such a process'for, the distillation of formic acid and thereby to avoid the difficulties which hitherto were connected with the preparation of formic acid and which have been described above.

As already mentioned it is not new to obtain in distillation processes an acceleration by leading an indifferent gas orthe like through the apparatus in a closed circuit. However, the industries in which this method of working has. become known are so far removed from the preparation of formic acid from formates that the application of this method of working for overcoming the difficulties inherent to the preparation of-formic acid was in no-way obvious.

WhatI claim as new and desire to secure by Letters Patent is T A process for the'preparation'of formic acid from the reaction mixture of formates and mineral acid by distillation, consisting in leading a current of a as indiiferent to the reaction mixture and 1ts final product, in a cyclic current through thewhole distillation apparatus and the reaction chamber connected therewith which are both closed off against the access of outer. air.

In testimony whereof I have signed my 7 name ,to this specification in the presence "of two subscribing witnesses. w

' Q JULIUS wEIsE;

. \Vitnesses: 1 i

ERNST Josnr Wesmormz, Inc LUowIojI-IUonnR'r. 

